Heat pumps are an efficient way to heat or cool a building and can be more energy efficient than traditional heating and cooling systems. In heating mode, the heat pump moves heat from a source of heat outside the building and introduces that heat into the building's heating system. In cooling mode, the heat pump moves heat from inside the building and relocates that heat out of the building. Heat is transferred to and from the building by pumping a compressible fluid through a heat exchanger. The heat exchanger is commonly configured as a series of pipes which have a large surface area for transferring heat. In many areas, above-ground air is an inadequate and unreliable source of heat for such pipes based on weather extremes, therefore it can be desirable to use subsoil pipes instead. This is an excellent choice for many areas where the pipes can be placed below the frost line such that the ground can act as a reliable near-constant source or sink for heat to allow for heating in the winter and cooling in the summer. Where available, the pipes may be submerged in a body of water. Doing so increases the efficiency to the system since heat is more readily transferrable with a liquid than with a solid such as soil.
The fluid housed in septic tanks and similar home wastewater treatment systems, is generally a higher temperature than the surrounding soil. Prior art systems have brought the heat transfer array pipes of a geothermal system in contact with the external area near a septic tank to benefit from heat within the septic tank. However, this can be expensive to install because many pipes will be needed around the septic tank to absorb heat from the tank. This can also be inefficient in areas where the ground is low in moisture content. Additionally, removing heat from the septic system alters the effectiveness of the bacteria which in turn reduces the efficacy of the treatment system.